Electrical musical instrument



Dec. 12, 1950- N. LANG-ER 2,533,821

ELECTRICAL MUSICAL INSTRUMENT Filed oct. 22, 1947 2 sheets-sheet 1 INVENTOR /Vrlmlas [digger BY M? HTTURNEY D ec. 12, 1950 N, LANGER 2,533,821

ELECTRICAL MUSICAL INSTRUMENT Filed oct. v22, 1947 2 sheets-sheet 2 Patented Dec. 12, 1950 l l 2,533,821 ELECTRICAL MUSICAL INSTRUMENT Nicholasv Langer, New York, N. Y., assignor, by vmesne assignments, to Central Commercial Industries,y Inc., Chicago, Ill., a corporation of Delaware Application October 22, 1947, Serial No. 781,377;

Clams. (CLM-1.19)v

The present inventionL relates.- to electrical musical. instruments, and, more particularly, to an electronic organ of novel and improved char-` acter.

AIn rmy U. S. PatentNo; 2,486,039 datedfOctober- 10, 1949, I have disclosed an electrical musical instrument which essentially comprises at least one `series of cascaded" aperiodicfrequency-halving trigger circuit stages 'and a master pulse generator supplying Vpulsesv of audio-frequency to one of said stages whereby output pulses of octavely related frequencies may be derived from the re'- maining stages. Inv general, trigger circuits of theEccles-Jordan type were found to be the most satisfactory for instruments' ofr the described character due to their simplicityof structure and their great reliability in,` operation; As 'is' Well known, in the EccleseJordan circuit a` pairr ofspace dschargetubes arel connectedvvith a net'- work. of capacitors and resistors'and a source of direct current potential in such a manner'that the circuit has tvvo` stable states of-equilibrium in which the two tubes are alternately` conducting. When a trainof negative pulses is applied tothe control grids of the two tubes, the conducting state is shifted from one tube to the other for each successive pulse; Pulses of one-half, of the frequency of the original input pulses may be derived from one of the tubesrofthe first stage and maybe applied tothe grids ofgthe tubes of the next stage, and'so forth. Thus, from a series of cascaded,Eccles-Jordan stages it is possibleto deriveoctavely. related output pulses having frequencies of f/Z, f/4, f/8, f/16, etc., when the frequency of the pulses aDpledto the'iir'stl stage is f. Althoughthe practical advantages of a gen eral-,ingV system of the4 described'v character are numerous andare fully set4 forth inmy aforesaid cofpending. application, perhaps the most important single advantage is: that. in the' resistorcapacitor networks associated with each stage the corresponding resistances and capacitorsA are of equal values. This greatly increases the simlplicity of .assembly in contrast to the presentv cascaded oscillator stages almost exclusively em- -ployed in conventional;electrioalmusical instruments Where each stage has to be individually tunedl to lits desired operating frequencyk by proper selection ofthe circuitcomponents.

The signals of octavely related frequencies obtainedl from c'ascadedv Eccles Jordan circuits are generally characterizedby a vvaveforrnV of square shape.A As is known'to' those skilled'in the'A art, l

theharmonic composition of'a`v square Wave may be represented bythe following formula:

complex wave is predicatedupon filtering outthe-l undesired harmonics from the said Wave;` this circumstance greatly reduced the number of dise' tinct" tone colors obtainable in. an` electronic organv employing EcclesJordan frequency dividing cir;

cuits;

I have nowdiscovered that this disadvantage may be fully eliminated and the outstanding lproblem may,- be solved in a remarkably simple mannen It is an object of the', present invention to.provide an electrical musical instrument having a system of generators originally producing square waves or other similar Waves comprising agenerally incomplete series ofl` harmonics which are converted into Waves characterized by a substantiall'yunbrokenseries'of harmonics.

It isanother object of the present invention to' provide an electronic organ comprising audiofrequency signal generators characterized by a square wave output which is converted into-a saw-tooth wave output suitable for conversion into musically valuable tone colors of great variety. l

The invention also contemplates an electronic organn of` novelv and improved character capable of producing audio-frequency signals ofV bothsquare and sawtooth Wave form which may be individually treatedby suitable filters for the prof duction of a practically unlimited range of tone colors simulating most ofthe conventional orchestral'instruments;

Other and further objects and advantagesaof the present invention will become apparent' from the following description, takenV in conjunction with the"accompanying'dravvings, in which Figures lj and 2 collectively constitute the cir'- cuit diagram of: an electronic organ, embodying they principlesL ofthe present invention.

Broadly stated, according'to the principles'of the present invention, signalsof squareuwaveflorm arerconverted into sawtooth waves byfcombiniirg several square `Waves havingoctavely relatedfrequencies and' predetermined relative amplitudes with respect to each other.

The frequency relationslfiipl of theharmonics of a square vvave follow like the odd numbers' of the series of integers: f

A square Wave` signal of twicethe frequency will have harmonics the frequenciesof which will relate to the fundamental frequency oflther'st series, asfollows:

A square wave signal of four times the frequency will have harmonics the frequencies of which will relate to the fundamental frequency of the first series, as follows:

Combining the foregoing three series, the following composite series will be obtained, omitting the harmonics above 23:

l, 2, 3, 4, 5, 6, 7, 9, l0, ll, 12, 13, 14, 15, 17, 18, 19, 20, 21, 22, 23

It will be noted that the series of harmonics is completely unbroken up to the eighth harmonic. Also, up to the twenty-fourth harmonic, the only harmonics absent are the eighth and the sixable in a practical and commercial electronic organ. Provided that the amplitude relation of the combined square wave signals of octavely related fundamental frequencies is properly selected, the result will be with very close approximation a sawtooth wave of the following harmonic composition:

I have discovered that the foregoing principle of producing complex Waves containing a substantially unbroken series of harmonics by combining octavely related less complex waves containing only the odd harmonics of their respective fundamentals is admirably suited for further improving the performance of electronic organs employing aperiodic frequency dividing trigger circuits of the general type disclosed in my aforesaid co-pending application.

Referring now more particularly to Figs. 1 and 2` of the drawing, the electrical musical instrument diagrammatically illustrated therein comprises a master oscillator M, a pulse Sharpener circuit P, five cascaded frequency-halving stages of the Eccles-Jordan type F-I to F--5, and an output circuit.

Master oscillator The master oscillator M is a generator of audio-frequency oscillations of a generally sinusoidal character and having a notably constant frequency.v It comprises a pentode tube T--fl havingA resistor connected between the control grid and ground in the conventional manner.

Tank inductance L--I is coupled to another smaller inductance L--2 connected between cathode I4 and Vground and providing feedback between the grid and cathode circuits. The tank circuit may be tuned by means of a powdered iron core I1 which is axially displaceable in inductance L I. A relatively large capacitor C--3 is connected between the hot terminal of the tank circuit and plate |0. Screen grid I2 is connected to the midpoint of two resistors Rf-3 and Rf-4 arranged between B plus lead I5 and ground lead I6 and is effectively grounded for audio frequencies through a bypass capacitor C-4.

As is more fully disclosed in Patent No. 2,489,- 497 to James A. Oswald, a circuit of the described character will produce electrical oscillations of a sinusoidal frequency determined by the circuit constants, particularly those of the tank circuit, the said frequency being conveniently adjustable by means of movable iron core Il. These oscillations may be frequency-modulated by applying an audio-frequency oscillation of a frequency of about 6 to 8 cycles per second to suppressor grid I I, to obtain a vibrato effect.

Pulse Sharpener circuit The function of the pulse Sharpener circuit P,

p 2| and a cathode 22, while triode T--2 comprises a plate 23, a control grid 24 and a cathode 25. Plates 20 and 23 are connected to B plus lead I5 through plate resistors R--II and R-|2, respectively, and cathodes 22 and 25 are connected zo ground through cathode resistors R|3 and R-|l|, respectively.

Output signal from the master oscillator is applied to triode T| through a network comprising a capacitor C-5 and resistor R--I5 serially connected between plate I0 of tube T-n and ground, their midpoint being connected to control grid 2| of tube T-I through a high resistance Rf-Il, acting as a grid limiter. Plate 20 of tube T-l is connected to ground through a differentiating network comprising a capacitor C--II and a resistor R-I'I, the midpoint of the said capacitor and resistor combination being directly connected to grid 24 of triode T--2. By suitable selection of the circuit constants more fully disclosed in the table forming part of the present description, it may be readily obtained that the sinusoidal oscillations derived from master oscillator M will appear in the form of sharp, welldeiined negative pulses at the plate 23 of triode T-Z. In view of the fact that pulse sharpening circuits of the described character are Well known to those skilled in the art and do not form part of the present invention, it will not be necessary to give a detailed description of their operation.

Frequency divider stages The frequency divider circuits, of which five, F--I to F-5, are provided in cascaded arrangement, have the function of dividing the input pulse frequency by the factor of 2 per stage.

Referring more particularly to frequency divider stage F-I it comprises a twin triode T-3, T-II. Triode T-3 has a plate 30, a control grid 3| and aicathode 32, triode, T--4 has a plate 33, a control grid 34 and a cathode 35. Plates 3D and 33 of the said twin triode are connected to B plus lead I 5 through plate resistors R--2l and Rf-22, respectively, cathode 32 is connected to Pla-te 3 Blf of tif-iode i 'T1-31"is` `connected Ito input point #6i-off thefrequencyL divider" circuit through serially .:ormectedA` resistors Rie-215* and Rf-ZB'. lilrewiseiplate -33' of triode- TJ-Mis connected to the same inputpoint`- 'f'thfrougf serially connecte edfresistors H-Z'Ifand'Pw-Zi Input-point is connected toa source= of negativefC" bias voltage (lead '31) through A-au resistorf'Rl-ZS GricrlV of"triodefT'--3 -is connected tothe-corn- Inon point of resistors R--21 and R-Z-andf grid 311'" ot'-"tri0de- T-4-is connected-*to thfccommon point` of resi'stors-='R'-25 l and E61-2 6i. Sina-il' :capacitors CLM 'and Cl-2v2 'areconnected across resisters :Rl-Ziand-"R-Z 1, respectively; forreasons whichiwill appear-presently:

Frequency divider circuits F'-21'1to=`F -5frespectively include tvvintriodes,y 'IY-5; lL-4i;l T'-1"`, 'PL-8;'-r- T-'-9, 'IL-|05 and? T-I I, 'IV-I2? The tube elmentse andthe circuit elements-oi'- these cirand" their" connections are identical" with those "of circuit Fi-I andL thereference-- numerals applied thereto have been derivedfrom the nu'- m'erals" ofthe respective elements in circuit F-I byaddingfl', 20; 30 andffthereto. In' View of theid'entical arrangement of the several frequency-A dividerci'rcuits; it `vvill lbe sufiicient todescribe the'operation of `the'flrst one; I:

Referring novve to' frequency;v divider circuit vlL-l in Figivv 1;- th-is Yisaf-modiiication vofthe WelI-known Eccles-Jordan trigger circuit in" which resistive networksiaref associated 'withY the 'elements'of two triodesein such i amanner 'thatat any--'time-- only oneeofffthe twotriodes'canbeconducting;` Thus,

assuming that triode 'IL-3 is initiallyconducting, the respective valuesfoffresistors R-ZL Rf-25, R-26 yand R-29f are so determined withrespect tothe B'and C'voltages andto.thetubereharacterf ist'cs that, a... negative-biasr beyond cutoff` will .be applied' t grid. Moi. triodefIf--ll maintaining the samejn the non-conducting state.. Likewise, should T-4 be. initially conducting, T-3 will be maintainedlin the non-c0nductingstate as a lresulto'f the symmetrical arrangement ofthe two resistivenetvvorks. Either oneof thesefstates will persist. indenitelyin the` absence of anexternai y signal.`

Againassuming .that triodaTs-ais'- conducting and that a; strongsnegative; pulseisappliedeto inputV point36, this pulseA wil-lhave noti appreciable eict:Ak uponz grid.- of' triode. T---4-'vvhicl'1 is already-biased negatively beyond cutoff; However, the-samer negative`v pulse simultaneously applied t'ofgridlv .of triode Tv-3 willA momentarily render it suiiciently negative to cut off thefplatercurrent of the said tube. As soon...as"thef platecurrent stops tonow-and the voltage. drop acrossresistor Riv-2 I` isigreatly reduced. grid 34 of..t,ube1Tj'-4Will ber-.rendered positive; sunicientlysoz asatofrender` tube Tf-Mconducting. This ein turn-will applyxa negative bias beyond cutonto grid 3110i" tube '13-3 maintaining vit in thev` nonconducting; state nitiatedby the negativefpulse; In'other words, af singlenegative pulse applied -to thef input :point 36rhas the. -efiectoftransferring I ther conducting state=from :one triodefto1 the other,v in :the:A instant cesefffrom -T-3 itoJI-A-.' Another 'negati-ve; pulse will?. again transfer; the' conductingn statel-v from TL-fback 'to T=.3. It will `be readily'v understood thata train. of "negative pulses-applied toi` point 36iw11'lcansethe conductingfstate:tofalternatebetween tubesl T-l-3 Tand T-fathalf: thefratef. ofthe `applied pulsesisosthatipulsesathaltrof thea-input f-requencmmayfbewithdraw-n;froxnreither;oneiof 61 tl-ief-tvvwtriodes; Thus-,f itz-Will .be seermthat:they circuitlvvirll function as a frequency divider; divide ingiany inputfrequencyiby thefactor'oiZs.

Condensers `C-Z I andv C--22, respectiyely'cons nected across resistances R-25-and`R-l-2i`l are eifective inY improving :the triggeringv enact inatl'iat they permit transmittal. of thefreversingipulses to they corresponding grids practically` instane taneously, without the delayiru;.effectA oftheeresiSl-l tors through which the pulses'hadrto travel 'inthe absence of the-'said capacitors.

While the: foregoing'eXplanatio-n offthe operationofr the rEccles.-Ji'irdantrigger circuitamerely approximates.' the. actually much morev complex dynamic conditions existing in circuits ofthe devscribed; character; it isiconsi'd'ered to bel-sufficient for the purposes of the present description; particularly asl thosefski'lled vin the art are" familiar with. the principles underlying to the operation of' circuits of this type.

The negative. triggering pulses' of ai: frequency f 'are applied to. thefrst frequency dividerstage F--I byf means of ai coupling capacitor C ZQ-i'confnected betvveenplate 23 "of/pulse sharpening tube T'2zand inputpoint 35S-oi 'triodesfT-S'and T-4. Pulses ofa. frequency f/2'are applied to frequency divider stage: iii- 21 by means of" a simi-lar coupling capacitor C-Zii" connected' tov grid 341- of'. triodef T--4- andy through lead' i9" to input'pointd of triodes Tl-E andv T--i Pulses ofY a frequency f/4' are applied to frequency divider stage F-3 cy means of capacitorJC-Ml c'onnectedfbetvveen. grid lillA of triode'vll Til-651 and input pointiV of 'triodesTL-l; 'IL-82 Pulscs ofi-'a frequency f/8 and /l'fare applied to'frequency divider stages F-liv andliF-Sgi respectively; by capacitors.y C-E' andv C'-6l'lconnected'between grids 54 and Se of triodes T-JB and T-Ylg respectively;andinputfpoints and T6 of tri'odes"T-'-9, T- I0 and` T`- ll l T- l?, respectively.

Itfhas been. noted in the foregoingithatall of the frequency divider' circuits F-IY tov FL-S-are identical in character and in their circuitf'arrangement and that thereference4 numerals of vthe=variousz circuit components and tubel elements have beenobtained from. tho-seof dividerl circuit F-l by adding I0' for each of ,thee circuits; All of the corresponding capacitorsgand resistorsfare of equal vvalue-inail divider circuits.; Althoughin thex drawinggonly ve Vfrequency dividers stages have been shown, any suitable `number:may'be employed and thes principle of frequency.l division maybe extended indefinitely. Thus; pulsesffofla frequency f/SZ maybe passed on to" anadditional stage; (notshown) through'leadl connected :to grid 14 of tube T-I2, etc. For example, in'an electronic organ covering thefmusical range fof '7 octaves, it will.' be generallynecessa-ryto provide 1. frequency divider stages, Y

Output circuit Output signal of octavely` related frequencies may be draw-n: from@ any' portion-` ofseachfreduencyv divider'- vstage.` In theT illustrated former of theinventiomthe output signal is obtained-across R53 These resistors are of relativelyloW-ivalue to' avoid .unbal-ancing the 'otherwise fully symmetrical arrangement ofthe Eccles-Jordan circuiti'al- I though; ifdesired; ae similar' cathode resistor'may i's'to be considered.: that theY signals drawn from tlreztwof. cathodes oft' each .stageflare 180 degrees out-of-phase. In general, lt is preferred, however, to draw the output signal from the cathode of the triode which does not supply triggering pulse to the next stage as this results in greater stability of the system.

The instrument of the invention permits producing both square wave signals and sawtooth wave signals which may be selectively utilized in order to obtain a greater variety of musically useful tone qualities.

The square wave output system comprises leads 80, 8|, 82, 83, 84 and 85 connecting cathodes 22, 32, 42, 52, 62 and l2 of tubes T|, T-3, T-'-5, T-|, T--9 and T-I I, respectively, to keying switches K-|, K-2, K-3, K-4, K- and K-G, respectively, through decoupling resistances Rf,-80, R-BI, lit- 82, R-83, R-84 and RHES, respectively. The working contacts of all of these switches are connected to square wave output bus bar O-l. ln this connection, it may be observed that the signal flowing through lead 88 is drawn from the pulse Sharpener stage P and is not a true square wave but a clipped sine wave. However, for all practical purposes the difference between the clipped sine wave and the square wave is not signicant for musical purposes and the described procedure of obtaining output signal also from the pulse Sharpener stage makes it possible to save one frequency divider stage in the instrument. The sawtooth wave output system comprises output terminals 90, 9|, 92, 93, 94 and 95. Of these:

Terminal 98 is connected to cathode 25 of tube T-2 through decoupling resistor R-90.

Terminal 9| is connected to output lead 8| through decoupling resistor R-Bl and to cathode of tube T-2 through decoupling resistor Rf-92 and lead 9G.

Terminal 92` is connected to output lead 82 through decoupling resistor R -93, to output lead 8| through resistor IRF-94 and lead 91 and' to cathode 25 of tube T-2 through resistor R--SE and lead 91.

lon.

vOf course, the system can be extended to further lower frequency stages, if such are provided, decoupling resistors R-l 05 and R-IOB and lead ||J| being illustrated for this purpose, connecting to an additional output terminal (not shown).

It will be readily observed that, in general, each output terminal is connected to three square wave output leads of adjoining octavely related frequencies through decoupling resistors of suitably 'selected values so that an approximately saw- 4tooth wave-Shaped signal will appear at such terminals. While terminal 90 is connected to only one output lead, the clipped, differentiated sine wave signal drawn will to some extent approximate a sawtooth wave shape. Also, terminal 9| is connected to only two output leads. However, the resulting absence of certain of the higher even harmonics will be hardly noticeable to the musi- .cal ear since many of the said harmonics are be- CTX yond the audible frequency range. The decoupling resistors associated with the same output terminal are of progressively decreasing values in order to approximate the relative amplitudesof the corresponding higher harmonics to the respective amplitudes of such harmonics present in a sawtooth wave. Thus, R-|02, R|03 and R-IM, connected to terminal 95 may have values of 50,000, 100,000 and 200,000 ohms, respectively, and terminals 94, 93, 92, etc. may have decoupling resistors of similar values associated therewith.

A normally open switch K-T, K-8, K-S; K-|0, K--II and K-IZ is connected between sawtooth wave output bus bar O--2 and output terminals 90, 9|, 92, 93, 94 and 95, respectively.

Square wave output bus bar O--I is connected through a normally closed switch K-l3' to three quality control or stop switches K-.|4, K-I5 and K-|B. The working contacts of the said three switches are connected to a main output bus bar O through quality lters QI, Q--2, Q--3 and decoupling resistors R-||0, R-III, R-I I2, respectively.

Sawtooth wave output bus bar O-2 is connected through a normally closed switch K--Il to three quality control or stop switches K-|8, K|9 and K-2U. The working contacts of the said three switches are connected to main output bus bar O through quality lters Q-'-||, Q-S. Q-B, and decoupling resistors R-|l3, Pf-IIL R||5, respectively. y

Main output bus bar O is connected to an amplier A and the amplified audio-frequency oscillations are converted into musical sounds by a loudspeaker S. i

Operation From the foregoing description, the operation of the electrical musical instrument embodying the invention will be readily understood by those skilled in the art. The circuit constants of master oscillator M are so adjusted that it produces sinusoidal oscillations of a frequency f which equals the frequency of one of the notes (for ex'- ample C) of the highest octave of the instrument. These sinusoidal oscillations are converted into sharp negative pulses of the samefre quency by pulse Sharpener circuit P. These pulses are introduced into the series of aperiodic, cascaded frequency divider circuits F--I to E-S so that pulses of frequencies f/2', f/4, f/8, f/IS and f/32 will appear in the respective cathode circuits. The result will be square wave-shaped signals of such respective frequencies at switches K--I to K-6, and sawtooth wave shaped signals of equal respective fundamental frequencies at switches K--l to K-|2.

Preferably, pairs of the said switches (K- l and K-l; K-2 and K8 K-3 and K-9; K-4 and K-IU; K-5 and K-I K-'E and K|2) are operable by the same key (B-L B--2, B-3, B-4, B--5 and B-E, respectively) of a playing manual, such mechanical connection being indid cated in the drawing by dotted lines connecting the respective coordinated switches. Upon depression of any key, both square wave and sawtooth waves of the same fundamental frequency are introduced into output bus bars O-I and O-2, respectively. The harmonic composition of the oscillations present is modified by the illters Q-l to Q-3 and Q-4 to Q-B, respectively, according to the open or closed condition of stop switches K|4 to K--IB and K-l to K-20. Thus, as illustrated in Fig. 2, lter Q-2 is eiectve as to the square wave output bus bar O-'I wave. Quality filters .suitable for the,purposesl ofitlieinventionare ,disclosed for example, UnS.. Patent N0. 2,403,664 ork in the Larsen-Patent No. ,2,4 03,090. I have .found that square wave-signals, upon appropriate filtering are particularly suitable vfor producing the ute andldiapason type @tone-Qualities, whereas l.sawtootli .waye-signalsupon appropriate lteringare particularly suitable, fof produoiiig the tone qualities, @of Y-strr,1g,. and ,reed instruments in an veleetronic organ ltwill .be noted that .in a complete -eleotroni organ `.1,2 s ystem'sof the type illustrated-:in Figs. 1- and .2 ,are,provided corresponding .to the 1 2 Steps of the equally tempered scale. In,ve wof the iaot thatall ,..o-f ,thesaid 12 `systems are l identical as ;to. their circuit. and operation and melelyf :differ the kfrequenoy of 'the master osoill'ators,.fit will .not be ,neessaryfto illus- .trataand to describe ,the same. QFor detai1s of suehvorgans reference may be 'had to .my aforesaid BatentI No12.,46,039. Oi course A the output 1111s. barssO-QL O- ffZ-,and aud theassociated filters,.stop.swithes, amplifier and speaker may :b e thesame ion 1all 1`2 notes ystem s` ina practieal electronic organ.

llheeleotical ylaluesof the elements ,as numhereiand letteredon. fthe drawings audseveral `circuits ...and networks; and preferred types j o'f yaeuumytubes ,employed .are approximately, was ollows:

.fsResistanoes yCondensers Tubes off theft; mriusfifoltaeeis about y 150Voltsin eloiif dispar ieg ifs-om ihovplcinoiiolssofths :ptessin'tixi-f,

@litio-r1. l considerall. of these var-iationsfarid modioatioriso soopeoof the adantedito p ioduoe: si11is0do1..-aiidisfre osoiliations of constant fireqiionoy, sharipsnemrsut t0 CQmrU said Dillsii'OEI-S 50 aflrtrairl'-i9fopll-1S IfleS o ascadedlaperiodio frequency-hai s nigger-oir uifstases resinasive itonsaidzpul es by thseliorationgof ootarely omplox-wate Lfoi'm oiiafraoisrcompositonfffromWhich-:seltytam ofttheeharmo ,arre 1,abser-1 t,1 a pluralityfof outputeterminalsaen dscouplmg elements :forislipplyimgosignalsffnomseleoted ,ifespeotiveisxoiinsof oetavelyaadjnining.-stages. .to eaeh of naisrmesultngin eomposite signals' 'wayeeinrm .at-.saidterminalssehanaete ized'iiqyta Ipractically.fniiiirokert series of harmonics L 2; In:. an eleotrioall musical instrument, :the combination whieheomprises r`@irrilaster oscillator adapted to ,-:produoe substantially sinusoidal aucuosfnequency oscillations of @onstaat ,ire-

quency, a pulse peaker circuit v ouvert-usaicl oscillationsrintoiatrainfohsha 4,loiilses,fasseries efseaseadedfarieriadic @seque @y halvingvaimait,stagesfoitheis'perespossivoto@saidsin Grishampulsesibyctheseneraton;oie-set of- Pils of eemulexi wave.fform eharaoteigizedybyQ ctavely. relatedffundamentalsiandpby,aeharmoniogfqnfipb# sitionoin which only the odd :harmonics ,are

present,faglpluralityaof output termiiialsandeonf 55 giusti-ye paths -fsiipplfymg sional -fr-omffselsotsd grousisof Gta ly'adioniisatrigaer oircuitfstaees toeaohy o .-terminals andi-makingavalablaat silohfiormuis-1s modiod signslsihsvngaooiiblox wave iormfaiid -inludaeapraotioally unbroken seriesfofgharmguics A eleotrial musieal:ipstrumerittheom- Whichcomprises a,-, master oscillatp lirodii s nusoidolconstant,audioffrouorio puiser peaker ,eircuit Iooiiiler'tirig into atraim of, sharpupulsesu assev I Nng trigger flfia sst of ootfvoly rslsiodssqusrofwavo u 4 toterminalsQand eoli- 1 enerallyfditerent:impedaiiee signalsat predetermined relativv ain- .p litudos-f fromssolootsd swims: sfrtrigger- :v :oirloiiit i1 the im@v 'spirit and volition, ss disclosed :in:

2,3"3 asa mental frequencies available at such terminals.

4. In an electrical musical instrument, the combination which comprises a plurality of generators producing octavely related audio-frequency oscillations of complex waveform characterized by identical but octavely transposed harmonic composition from which certain of the harmonics are absent, a plurality of output terminals, and a plurality of coupling elements for each of said terminals respectively connected between the terminal and an output point of a corresponding generator sequentially selected from a group of octavely adjoining` generators of increasingr frequency, the rst one of said elements supplying from the lowest frequency generator to the terminal signal of complex wave form from which certain of the harmonics are absent, and the others of said elements additively supplying from the higher frequency generators to said terminal signals of complex wave form including substantially all of said absent harmonics whereby the resultant composite signals of complex wave form at each of said terminals will be characterized by a practically unbroken series of harmonics.

' 5. In an electrical musical instrument, the combination which comprises a plurality of sources of octavely related audio-frequency oscillations of complex waveform characterized by the presence of the odd harmonics and by the absence of the even harmonics, a plurality of output terminals, and a plurality ofconductive paths for each of said terminals respectively connected between the terminal and an output point of a corresponding source sequentially selected from a group of octavely adjoining sources, the first if having a substantially square wave output, a plurality of output terminals, and a plurality of conductive paths for each of said terminals connected between the terminal and a group of octavely adjoining sources, the rst one of said paths having such impedance as to supply square wave signal of predetermined amplitude from the lowest frequency source to the terminal, and the others of said paths having such impedances as to supply square wave signals of progressively decreasing amplitude from the higher frequency sources to said terminal, the relative impedances of said paths being so adjusted as to additively combine the octavely related square wave signals into a wave form practically approximating a Vsaw tooth wave at said terminal.

" 7. In an electrical musical instrument, the combnation which comprises a plurality of sources of complex audio-frequency oscillations the fundamentals of which decrease as the successive powers of 2 and the harmonic composition of which is substantially restricted to odd harmonics, an output terminal for each of said sources, and a plurality of resistive paths for each of said terminals respectively connected between the terminal and an output point of a corresponding l2 source sequentially selected from a group o octavely adjoining sources, the first one of said paths supplying from the lowest frequency source to the terminal signal of complex waveform from which the even harmonics are absent, and the others of said paths additively supplying from the higher frequency sources to said terminal signals of similar but octavely transposed complex' Wave form including substantially all of said even harmonies thereby to produce at the terminals output signals characterized by a series of harmonics which is unbroken up to a certain limit harmonic, said limit harmonic being determined by the number of sources to which each terminal is conl5 nected by said plurality of resistive paths.

8. In an electrical musical instrument, the combination which comprises a series of sources of complex audio-frequency oscillations the fundamentals of which decrease octavely and the harmonic composition of which is substantially restricted to odd harmonics, a series of output terminals, and a set of three resistive paths for each ci said terminals respectively connecting the corresponding terminal to the output points of three oi said sources adjoining to each other in the series thereby to produce output signals of complex waveforms at such terminals, the fundamental of each of said signals equaling the fundamental of the source of the lowest frequency to which the corresponding terminal is connected and the harmonic composition of said signals being characterized by an unbroken series of harmonics at least up to and including the seventh harmonic. Y

9. In an electrical musical instrument, the combination which comprises a plurality of sources of octavely related audio-frequency oscillations of complex waveform characterized by the substantial absence of the even harmonics, a plurality of output terminals, a plurality of conductive paths for each of said terminals respectively connected between the terminal and an output point of a corresponding source sequentially selected from a group of octavely adjoining sources, the iirst one of said paths supplying from the lowest frequency source to the terminal signal of complex wave form from which the even harmonics are absent, and the others of said paths additively supplying from the higher frequency sources to said terminal signals of similar but octavely transposed complex wave form including substantially all of said even harmonics thereby providing at said terminal a modied signal of complex wave form including a practically unbroken series of harmonics up to a desired harmonic,I an output circuit, and switches interposed between said terminals and said output circuit to render said modiiied signals selectively effective in said output circuit.

l0. In an electrical musical instrument, the combination which comprises a series of sources of octavely related square wave oscillations of audio frequency, a plurality of output terminals, resistive paths supplying square wave. signals at predetermined relative amplitudes from selected groups of octavely adjoining sources to each of said terminals and combining such signals into octavely related sawtooth wave signals at the several terminals, an output circuit, a key-controlled switch interposed between each of said terminals and said output circuit adapted when actuated to render said sawtooth wave signals selectively effective in said circuit, a sound producing means, and a lter network connected between said output circuit and said sound pro-v ducing means to change the harmonic composition of the signals applied to the sound producing means.

11. In an electrical musical instrument, the combination which comprises a series of sources of octavely related square wave oscillations of audio frequency, a plurality of iirst output terminals, a conductive path connected between each rst terminal and a corresponding source supplying square wave signal of predetermined frequency to said first terminal, a plurality of second output terminals, a set of conductive paths for and connected between each second terminal and a corresponding group of octavely adjoining sources and having such relative impedances as to additively combine the square wave signals drawn from said group of sources into a saw tooth wave at the said second terminal, an output circuit, and a key-controlled switch interposed between each rst and second terminal and said output circuit adapted when actuated to render signals of different wave form and of different frequency selectively effective in said circuit.

12. In an electrical musical instrument, the combination which comprises a series of sources of octavely related square wave oscillations, a plurality of first output terminals, a resistive path connected between each rst terminal and a corresponding source supplying square wave signal of predetermined frequency to said first terminal, a plurality of second output terminals, a set of resistive paths for and connected between each second terminal and a correspond ing group of octavely adjoining sources and having such relative impedances as to additively combine the square Wave signals drawn from said group of sources into a saw tooth wave at the said second terminal, a square wave output bus bar and a saw tooth wave output bus bar, a switching key interposed between each first terminal and said square wave bus bar and between each second terminal and said saw tooth wave bus bar adapted when actuated to render square and saw tooth wave signals of different frequencies eifective in the respective bus bars, a main output bus bar, and filter networks connected between both the square and the saw tooth wave bus bars and the main output bus bar to transfer signals of modified harmonic composition to said main bus bar.

13. In an electrical musical instrument, the combination which comprises a plurality of sources of octavely related square wave oscillations, an output terminal for each of said sources constituting a rst set, coupling elements for connecting each of said' sources to the corresponding terminal, a second set of output terminals, coupling elements supplying square wave signal at predetermined relative amplitudes from selected groups of octavely adjoining sources to each of said secondset or" terminals and combining such signals into octavely related saw tooth wave signals at the several terminals, a preliminary output bus bar for each of said sets of terminals, a switch connected between each terminal of both sets and their respective preliminary output bus bars, a key for each pair of switches coordinated to square and sawtooth 14 wave signals of equal fundamental frequency adapted when actuated to render square and sawtooth wave signals of corresponding frequency simultaneously effective in their respective preliminary output bus bars, a main output bus bar and a switch and coupling elements connected between each of said preliminary output bus bars and the said main output bus bar to make signals or" square and sawtooth waveform selectively effective in said main output bus bar.

14. In an electrical musical instrument, the combination which comprises a plurality of sources of octavely related square wave oscillations, a square wave and a sawtooth wave terminal for each of said sources constituting a pair, a resistive path connecting each of the square wave terminals of said pairs to its corresponding source, a set of resistive paths connecting each of the sawtooth wave terminals of said pairs to a selected group of octavely adjoining sources, a square and a sawtooth wave preliminary output bus bar, a switch connected between each oi. said terminals and their respective preliminary output bus ba s, a key for each pair of switches adapted when actuated to render square and saw tooth wave signals of corresponding frequency simultaneously effective in their respective preliminary output bus bars, a main output bus bar. a plurality of iilter circuits, and switching means for selectively connecting said iilter circuits between said preliminary and main output bus bars to make signals of modified harmonic composition eifective in the main output bus bar.

15. In a system for synthetizing sawtooth wave currents from square wave currents, the combination which comprises a plurality of sources of square wave currents the frequencies oi which are respectively proportional to successive powers of 2, an output circuit in common for said sources, and a coupling element for each of said sources interposed between the correspending source and the said output circuit, the rst one of said coupling elements having such impedance as to supply square wave current of predetermined amplitude from the lowest frequency source to said output circuit, and the other coupling elements having such impedances as to supply square Wave currents of progressively decreasing amplitudes from the higher frequency sources to said output circuit, the relative impedances of said coupling elements being s0 determined with respect to the original amplitudes of the square wave currents generated by said sources as to additively combine said square wave currents in said output circuit into an approximate sawtooth wave current.

NICHOLAS LANGER.

REFERENCES CITED The following references are of record in the iile of this patent:

UNITED STATES PATENTS Number Name Date 2,171,536 Bingley Sept. 5, 1939 2,233,258 Hammond Feb. 25, 1941 2,233,948 Kock Nov. 4, 1941 2,301,869 Hammond et al. Mar. 10, 1942 2,403,090 Larsen July 2, 1946 

